Low water content in the mantle source of the Hainan plume as a factor inhibiting the formation of a large igneous province
Low water content in the mantle source of the Hainan plume as a factor inhibiting the formation of a large igneous province
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海南地幔柱地幔源区含水量低是抑制大型火成岩省形成的因素
DOI：
10.1016/j.epsl.2019.03.034
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发表时间：
2019-06-01
影响因子：
5.3
通讯作者：
Wang, Qin-Yan
中科院分区：
文献类型：
--
作者：
Gu, Xiao-Yan;Wang, Piao-Yi;Wang, Qin-Yan
大火成岩省（LIPS）通常被认为与地幔柱有关，并且对地球历史上的超大陆分裂事件、气候变化和生物进化具有重要意义。 LIP 的高熔体生产率可以在严格的熔化条件下实现：异常高温、大幅减压、添加易熔成分或显着富集水。尽管人们多次注意到显生宙LIPs中出现了富水现象，但地幔源区富水对于LIPs生成的意义尚未明确凸显。东南亚玄武岩省（SABP）被认为是由含辉石岩源的海南地幔柱形成的，在28.5 Ma到全新世的很长一段时间内，在约0.037 Mkm（2）的小区域内侵位，因此与典型的LIP（> 0.1 Mkm（3））在小于5的一个或多个脉冲中侵位的体积不同。 马）。在这项工作中，我们测量了海南岛北部（SABP 的一部分）新生代玄武岩中高 Mg# 单斜辉石斑晶 (12-179 ppm H2O) 的 H2O 含量。这些数据被用来估计这些玄武岩地幔源的水含量，产生的值在 84-360 ppm H2O 范围内，这明显低于许多显生宙 LIP 获得的值（数千 ppm）。通过计算海南玄武岩的地幔位温比 MORB 源地幔高约 170 ℃，我们认为源水的缺乏可能降低了熔体生产力和地幔柱上涌的速度，并导致海南地幔柱在 350-500 km 深度失速，抑制了海南地幔柱形成 LIP，尽管发生了 其他有利条件。因此，SABP 的结果为地幔源区水富集在 LIP 形成中的重要性提供了证据。海南羽流中的低含水量可归因于经历了严重脱水的俯冲板块的结合。 (C) 2019 Elsevier B.V. 保留所有权利。
Large igneous provinces (LIPS) are generally considered to be related to mantle plumes and to have a great importance to the supercontinent break-up events, climate change and biological evolution over Earth's history. The high melt production rates of LIPs can be achieved under rigorous melting conditions: an abnormally high temperature, substantial decompression, addition of fusible components, or remarkable enrichment in water. Although it has been repeatedly noticed that water enrichment has occurred in many Phanerozoic LIPs, the significance of water enrichment in the mantle source for the generation of LIPs has not been explicitly highlighted. The southeastern Asian basalt province (SABP), which is thought to have formed by the Hainan mantle plume from a pyroxenite-bearing source, was emplaced over a small area of about 0.037 Mkm(2) over a long period of time from 28.5 Ma to Holocene, thus differing from a typical LIP (>0.1 Mkm(3) in volume emplaced in one or multiple pulses of less than 5 Ma). In this work, we measured H2O contents of high-Mg# clinopyroxene phenocrysts (12-179 ppm H2O) from Cenozoic basalts in the northern Hainan Island, which is part of the SABP. These data were utilized to estimate the water content of the mantle source of these basalts, yielding values in the range of 84-360 ppm H2O, which are significantly lower than those obtained for many Phanerozoic LIPs (thousands of ppm). After calculating the mantle potential temperature for the Hainan basalts about 170 degrees C higher than that for the MORB source mantle, we consider that the paucity of source water likely depressed the melt productivity and the velocity of plume upwelling, and induced the Hainan plume to stall at depths of 350-500 km, inhibiting the formation of a LIP by the Hainan plume, despite the occurrence of other favorable conditions. Hence, our results from the SABP provide evidence for the significance of water enrichment in the mantle source in the formation of LIPs. The low water content in the Hainan plume can be attributed to the incorporation of subducted slabs that had experienced significant dehydration. (C) 2019 Elsevier B.V. All rights reserved.